As industry has continued to refine and improve production techniques and procedures, corresponding requirements have been observed for placing identifying or data related markings upon components of manufactured assemblies. With such marking, the history of a product may be traced throughout the stages of its manufacture.
A variety of product marking approaches have been employed in the industry. For example, paper tags or labels carrying bar codes or the like may be applied to components in the course of their assembly. However, for many applications, tags, labels, and the like will be lost or destroyed. Ink or paint spraying of codes such as dot matrix codes are employed for many manufacturing processes. However, where the production environment is too rigorous or subsequent painting steps are involved, such an approach will be found to be unacceptable.
The provision of a permanent or traceable marking upon hard surfaces such as metal or plastics traditionally has been provided with marking punches utilizing dies which carry a collection of fully-formed characters. These "full face dies" may be positioned in a wheel or ball form of die carrier which is manipulated to define a necessarily short message as it is dynamically struck into the material to be marked. As is apparent, the necessarily complex materials involved are prone to failure and full face dies exhibit rapid wear characteristics. Generally, the legibility and abrasion resistance of the resultant marks can be considered to be only fair in quality. Additionally, the marking punch approach is considered a poor performer in marking such surfaces as epoxy coatings and the like.
Laser activated marking systems have been employed, however, the required equipment is of relatively higher cost and the abrasion resistance and "readability after painting" characteristics of laser formed characters are considered somewhat poor.
In the recent past, a computer driven dot matrix marking technique has been successfully introduced into the marketplace. Described in U.S. Pat. No. 4,506,999 by Robertson entitled "Program Controlled Pin Matrix Embossing Apparatus", the marking approach employs a series of seven tool steel punches which are uniquely driven using a pneumatic floating impact concept to generate man-readable and/or machine readable dot codes. Marketed under the trade designation "PINSTAMP", these devices carry the noted tool steel punches or "pins" in a head assembly which is moved relative to the piece being marked in selected skew angles to indent a dot or pixel defining permanent message or code into a surface of the marked component. The approach enjoys the advantage of providing characters of good legibility as well as permanence. Further, a capability for forming the messages or codes during forward or reverse head movements is realized. The device provides dot matrix characters of good abrasion resistance, good permanence and legibility, and is, advantageously, capable of marking upon such surfaces as epoxy coatings. Use of this basic dot matrix character stamping device is limited, however, to piece parts which are both accessible and of adequate size.
Robertson, et al., in U.S. Pat. No. 4,808,018, issued Feb. 28, 1989, describes a dot matrix character impact marking apparatus which advantageously is capable of forming messages or arrays of characters within a very confined region. With this device, a linear array of marker pins is moved by a carriage in a manner defining an undulating locus of movement. This locus traces the matrix within which character fonts are formed by the marker pins. The carriage and head containing the marker pin are pivotally driven by a cam to provide vertical momement and by a Geneva mechanism to provide horizontal movement. Pixel positions for the matrices are established by a timing disk and control over the pins is provided by employing an interrupt approach. Each marking pin within the head assembly of this advantageously portable device is capable of marking more than one complete character for a given traverse of the head between its limits of movement.
The demonstrated success of the above-noted pivoting head pinstamping apparatus has lead to additional calls on the part of industry for smaller, lower weight and faster impact marking devices. Additionally, with the need to provide more data in conjunction with marking, a need has arisen to develop a technique for marking multiple lines of characters and providing for variable character size. In addition to a call for a device providing these advantages, a continuing need exists for developing a device which is of lower cost; employs fewer parts, and has an advantageously modular and easily altered and repaired structuring.
Further, with the development of smaller characters and multiple lines of such characters, it is important that the pixel formation or indentations developed by such devices be of consistently uniform and proper font design alignment. The latter criteria should be evolved without the expenditure of undue calibration time during the course of assembly of such devices.